Like Qwyjibo said, it's definitely not necessary to play the previous games. This was my first Bioshock and everything still played out wonderfully. I will say, it might help to come into things with an open mind. I made myself buy into things from the get-go, and that made the experience that much more enjoyable (as opposed to being pessimistic and insisting the game "wow" me).

Well, I'm going to have more free time on my hands this summer than usual, so I may just buy both Bioshock games and play them.